Thunderhawk Blue vs Greatcoat Grey

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Greatcoat Grey is a little lighter, more muted, warmer than Thunderhawk Blue.

Can I use Greatcoat Grey instead of Thunderhawk Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Greatcoat Grey is a little lighter, more muted, warmer than Thunderhawk Blue.

Can I use Thunderhawk Blue instead of Greatcoat Grey?

The same difference applies the other way round: Thunderhawk Blue is a little darker, more saturated, cooler.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.